In mounting a flip-chip semiconductor chip face-down on a substrate, an underfilling technique is widely adopted. An example of the underfilling technique is a method of mounting a semiconductor chip on a substrate, and then filling a resin composition into a gap between the substrate and the semiconductor chip to seal the gap.
Along with the narrowing of pitch between bump electrodes, the pre-applied system attracts attention as an underfilling technique. In the pre-applied system, for example, a substrate having conductor wiring, a semiconductor chip having bump electrodes, and a thermosetting acrylic composition for sealing that is liquid at room temperature are prepared. The acrylic composition for sealing is disposed on the substrate, and the semiconductor chip is disposed on a position of the substrate on which the acrylic composition for sealing is disposed while the bump electrodes are disposed on the conductor wiring. In this state, the acrylic composition for sealing and the bump electrodes are heated for curing the acrylic composition for sealing to form a sealing material while electrically connecting the bump electrodes to the conductor wiring (see International Publication No. W02013/035871).
This pre-applied system is capable of simultaneously achieving mounting of the semiconductor chip on the substrate and sealing of the gap between the semiconductor chip and the substrate. Moreover, even if the pitch between the bump electrodes is narrow, unfilling of the gap between the semiconductor chip and the substrate with the sealing material is unlikely to occur.
Known pre-applied underfilling techniques include, in addition to a technique of directly using a composition that is liquid at room temperature (non-conductive paste process, also referred to as NCP process), a technique of using a sheet material obtained by drying or half-curing a composition (non-conductive film process, also referred to as NCF process) (see Unexamined Japanese Patent Publication No. 2011-140617).